I can shed a bit of light on those concrete sections, they were iron plates with a concrete layer on the top that were placed over the horse racing track after the horse racing fences had been taken down between meetings.
Eventually the club got tired of all the work involved and the club abandonned the track when the betting agency's made more money for the club than the race track.
Chevron publishing did a run of Australian touring car races, with the majortiy of races on the DVD's at Warick Farm, I'll check my collection as one dvd has Graham Hill narrating a lap of Warick farm at track level.
edit- Found it!
That's an absolutely fantastic video and will help enormously! Great info about the crossings too... Many thanks!